npalen
Elite Member
So, considering that it takes only 45 lbs of force to "pull" the 2" diameter cylinder, what is to keep one from pulling the cylinder full stroke or the rod clear out of the cylinder in the case of a single acting no gland?~45lbs is simply atmospheric pressure, applied to a to a ~3inch diameter circle. Yes, that stays ~constant. We *are* starting to get to spherical cows, and TBC that's not my area
How far does it have to move? That depends entirely on the assumptions we have to apply to simplify the problem enough to post these ~qualitative answers
> Pressure = APysicsConstant * Temperature_Kelvin / Volume
So if you double the volume, you half the pressure. This is "ideal gas law" and it's very accurate estimate for "everyday" temps & pressures.
So the 45lbs exists no matter what on the end we're assuming is fluid "free" to flow in and out (eg NOT up against a valve like LD1 points out). And lets say the cylinder is bottomed-out blind, with "negligible" fluid on the blind end. That fluid on the blind end is also starting atmosphere (if the rod is motionless and our above assumption hold).
So you start to pull. The blind end cavitates. You assumed it has "negligible" contents, so we moved from "zero" volume to "more than zero" - an infinite increase. The force would basically jump up immediately to that ~45psi.
Ignoring static & dynamic friction, and lots of other stuff. But yes, with respect to the pressures acting on the 3sqin of piston, it's that simple.
Edit:
A discussion similar to ours. The last post is interesting.
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